You will note from the outline of the structure of an essay shown earlier that paragraphs are the main components of an essay and that each paragraph has a topic sentence. Topic sentences then function relative to paragraphs exactly as thesis statements function relative to essays. Both provide the main idea of the text to follow in a clear, concise manner. Therefore, we can modify the definition of a topic sentence: a topic sentence is one clear sentence that states the main idea of any paragraph and provides a major supporting point for the thesis statement of the essay.